Process of making hydrated oxid of lead.



.UNITED STATES PATENT OFFICE JAMES-TH. BRIDGE, or New roan, N. 1:, an!) CARLE'LON aLLls. or Bos roN, MASSACHUSETTS, AssieNoas, BY MESNE ASSIGNMENIS,

OF ONE- THIRD TO SAl-VYER, FOSilElt "MASSACHUSETTS, A. FIRM.

AXII) HARDY, OF BOSTON,

; "PROCESS OF MAKING HYDRATED OXID OFILEAD.

, No. 811,552. ,I

Specification of Letters Patent.

Patented Feb. 6, 1906.

Application filed March 14. 1904. Serial No. 198,013.

v State of New York, and CARLETON ELLIS, of

Boston, in --the'county of Suffolk and Commonwealth of Massachusetts, have invented certain. new and useful Improvements in Processes for Making Hydrated Oxid of Lead, of which the following is a specification. I The usual method of converting metallic lead into the hydrated oxidof lead consistsin the dissolution of-the metal in an acid which forms a soluble lead salt and in subsequently adding to the lead-salt solution an alkaline hydroxid to precipitate the lead as hydrated oxid, his procedure gives rise to a by productof low value-n am ely, the salt fonned y the alkaline base with the acidemployed. For instance, the'solution of lead in nitric acid and precipitation by caustic soda yields a byproduct of nitrate of soda Whose market value is much less than that of the acid and alkali-consumed in the process.

It is the object of our invention to produce the hydrated lead by a method which eliminates the formation of waste products, but

which blyfits-cyclic action re-forms the active materia s as rapidly as they are consumed. For this purpose we employ the electric current. It is well known that if saline matter is electrolyzed in aqueous solution, using a metallic anode, that with a suitable curren t the metal is dissolved to form a'salt of the acid set free by the electrolysis of the saline electrolyte. With an anode of lead dissolving under such conditions We have found that an electrolyte containing the salt of an alkali or alkaline earth by the formation of free alkali y at thefcathode during electrolysis and by the subsequent diffusion and mingling of-the ano lyte and eatholyte brings about the formation and precipitation of hydrated oxid of lead in an amorphous condition. The vari-- ous attempts to produce hydrate of lead by electrolytlcal means have proven unsuccessful heretofore, because the electrolyte chosen e. 91, sodium nitrate.

either has been too costly-e. 9., sodium-acetate-+or has been liable to decomposition, thereby giving rise to complicated reactions and impairing the efficiency of the process- The electrolyte which we employ is sodium chlorid, which is quite free from iron.

neither costly nor liable to undergo secondary reactions. Depending on these principles, our process resolvesitself into'the following elements: the introduction into a saline solution of .a mass of lead to serve as anode and of a conducting body of inditferent material to act as cathode. Upon passage of an electric current through the solution lead dissolves and its preclpitationas hydroxid is accomplished in situ. For best results the followmg conditions obtain: The

anode should be of a good quality of lead v Ordinary pig-lead is usually suitable. It need not be cast to any pig form will serve. The cathodemay be'of any good conducting material unaflected by alkaline liquors. Lead, platinum, or graphite are serviceable. The electrolyte should con tain sodium chlorid or purified brine and should be heated to prevent the precipitation of lead chlorid during the electrolysis.

The following is an example of our method for the production of hydroxid of lead: "A current of twenty amperes per square foot of anode surface with an electromotive force of six volts was passed tlu'ough an electrolyte of hot brine of 10Baum gravity. A bar of lead constituted the anode; a carbon rod, the cathode. Soon after starting electrolysis a White precipitate began to form between the electrodes and graduallyincreased in amount. It slowly settled to the bottom of the cell, Where it was collected. At the close of the operation the lead anode had lost twentyseven grams in weight, while the precipitate of hydroxid of lead weighed thirty grams. The reactions which took place may be ex pressed as follows:

. ZNaCl electric current 2Na 201. 2Na 2H,,O 2NaOH 2H. 2C1 Pb PbCl.,. PbCl 2NaOH PbO H ZNaCl.

From these reactions it will be seen that the process is cyclic as regards the electrolyte. The net result of the process is the formation of hydroxid of leadl It is necessary to employ a hot solution of,

the electrolyte in order to obtain a pure hydrate of lead. Lead chlorid or oxychlorid special shape for the purpose. Lead in the lead anodes, ,of hot aqueoussolutions of purilied hrinefin mingling the-products ol'sziid" eleetrolysis; and m separating the sodormed lrVdrnted-oxid of lead.

- 12; Proeess'lonmaking hydrated o .\'id of lead \vhiehmonsists in the electrolysis, with lead anodes, ofhoteoneentratmlsolutions ofsodium ehlorid; in mingling .the anolyte and eatlmlyte;.in removing from thefelectrolyte the insoluble lead eompolrmls therehy l'ormed;

electrolytie eell. I

and in returning" tlio'said eleelrolytefto the Process for'vmaking hydrated oxid of lead which consists in tlw'eleflrolvsis, with lead anodes, of hot aqueous solutions ol'sodium ehlorid 1in mingling the .molyt'e and eat-holyte; in separating from the electrolyte the. so-formed hydroxid of lead; and in bringing the said electrolyte. again into the region of eleetrolytie action. I

4. Process forthe'continuous pl'odnetion of hydrated oxid of lead which consists in the electrolysis, with lead 'an0(]$" Uf a hot aqueous solution ofsodium 'ehloridfin eonnningling the anolyte and eat-holy-te to prodnee hy dratedoxid of leadan'd to re-form the original eleetl olyte f in r'emorin i therefrom the insolu- :hle' lead eon'ipounds; and in againsubjecting the said eleetrolvte to aforesaid eleetrolrsis.

in testimony ivhereotwe ha e-allixed our 7 signaturesinpresenee'ol'tufoyfitnesses. r

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